Panaflo fans and summing decibels.

[Duncan]

And here I'd thought Panaflo was dead. =) I've happened upon a new bunch of fans that may save me from fan-induced headaches forever.

I found them http://www.panasonic.com/industrial_oem/computer/computer_fans_panaflo_axial.htm on Panasonic's website. Incredibly low deicbels for the CFM they put out. www.caseetc.com has them at a reasonable price, too.

However, I've got a dilemma. I don't know whether to order 2 92mm fans or a single 120mm. The 92mm are 42.7CFM @ 27.0dbA, and the 120mm are 68.9CFM @ 30.0dbA, or alternatively 86.5CFM @ 35.5dbA.

The problem is this: which combination of fans will be the quietest? ie. how many decibels is 27.0 + 27.0? I know that decibels are logarithmic, but I can't remember my grade 12 maths. =P

If you could point me towards a calculator, or give me a method, that would be great.

Thanks!

 

[Tonec]

Heres where I ordered mine

 

[Jhhnn]

This is the fan math formula I picked up on Ars Technica:

loudest fan + log(10^(dB fan_type1/10) + 10^(dB fan_type2/10) + ... + 10^(dB fan_typeN/10))<

It may/may not be correct, for all I know.

The YSTech on the alpha is louder than any of the quiet panaflos, and will be the determining factor.

The easy way, of course, is to select fans that actually fit your case in the first place....

 

[Duncan]

Thanks! Ars is usually right on the money... great bit of help.

My intention was to take one of the very quiet 80mm case fans I had, and make a fandapter for my Alpha. That'll get rid of the noisy little ah heck, and probably drop my CPU temps by a few more degrees. However, I will have to cut new holes for the 92/120mm fans; my case only takes 80s and 60s. Addtronics has since fixed this little design flaw, but too late for me. =(

Tonec: did you find that using Dynamat or whatever other kind of acoustic foam you have noticeably dropped the sound level? I've heard conflicting stories on this... Also, some crazy guy reccomended *carpetting* the entire inside the the case. He said it raised his temps by could of degrees, but almost killed the noise. heh

 

[skriefal]

27 db + 27 db = 30 db

i.e. a doubling in sound-pressure level adds 3db...

 

[Tonec]

Tried dynamat and it works well if vibration is causing the noise. Accoustic foam by itself works for blocking the whine of certain fans. Actually if you have a case with failry thick, replacing the ps fan makes the most noticeable difference. Make sure its accoustic foam not just regular packing foam. You can by vinyl dampener+1/2 accoustic foam with adhesive backing but its not cheap.